The present invention relates to a rotary type regenerative heat exchanger, and in particular, to a rotary type regenerative heat exchanger which is applicable to a steam power plant, an internal combustion engine or the like.
Conventionally, there has been known a rotary type regenerative heat exchanger which is called as an air heater for preheating a combustion air in a boiler or the like. A structure of the conventional rotary type regenerative heat exchanger will be explained below with reference to FIG. 6 and FIG. 7.
As shown in FIG. 6, a rotary type regenerative heat exchanger 1 includes a cylindrical rotor 4 rotating around a central shaft 2, and a housing 6 arranged so as to house the rotor 4. The rotor 4 is provided with a heat accumulator 8 which repeats accumulation and radiation. An upper portion of the housing is provided with an air outlet duct 10 at the right-hand half portion, and a gas inlet duct 12 at the left-hand half portion. On the other hand, a lower portion of the housing 6 is provided with an air inlet duct 14 at the left-hand half portion, and a gas outlet duct 16 at the right-hand half portion.
In the rotary type regenerative heat exchanger 1 thus constructed, when the rotor 4 rotates, the heat accumulator 8 is alternately exposed to an air A and a gas G, and then, repeats an operation of accumulating a heat of the gas and radiating it to the air A, and thereby, the heat of gas G being recovered into the air A.
For example, in a steam power plant, the aforesaid rotary type regenerative heat exchanger 1 is arranged as shown in FIG. 7. In FIG. 7, the air A, which is a combustion air supplied to a boiler 18, is supplied into the rotary type regenerative heat exchanger 1 by means of a fan (not shown), and then, is supplied to the boiler 18 after the temperature of air A rises by a heat exchange made by the rotary type regenerative heat exchanger 1. A part of the gas G discharged from the boiler 18 is again returned to the boiler as a re-circulating gas GR by means of a circulating gas fan 20. On the other hand, the remainder of the gas G is supplied to the rotary type regenerative heat exchanger 1, and then, the temperature of the gas G is lowered by making a heat exchange with the air A. Thereafter, the gas G is supplied to a chimney stack (not shown) so as to be discharged to the atmosphere.
In the rotary type regenerative heat exchanger 1 shown in FIG. 7, an inlet air pressure (Pai), an outlet air pressure (Pao), an inlet gas pressure (Pgi) and an outlet gas pressure (Pgo) have the following relationship.
Pai&gt;Pao&gt;Pgi&gt;Pgo
As is evident from the above relationship, in the rotary type regenerative heat exchanger 1, various leaks of the air A and the gas G are generated by the difference in pressure between the air side and the gas side.
These leaks include the following leaks. More specifically, there are a high temperature radial leak (HRL) which is generated in an upper end face of the rotor 4 on the inlet and outlet of the air A and the gas G, a low temperature radial leak (LRL) which is generated in a lower end face of the rotor 4 (see FIG. 7), a post leak (PL) which is generated around the central shaft 2 of the inlet and outlet of the air A and the gas G, an air bypass leak (ABL) which bypasses a space between the rotor 4 and the housing 6 on the air side, an gas bypass leak (GBL) which bypasses a space between the rotor 4 and the housing 6 on the gas side (see FIG. 7), and an axial leak (AL) which flows from the air side to the gas side in the space between the rotor 4 and the housing 6.
In order to reduce these leaks, as shown in FIG. 6, the conventional rotary type regenerative heat exchanger 1 is provided with the following seals at the rotor 4 side; more specifically, a radial seal 22 which radially extends so as to seal a space between the air side and the gas side in the upper and lower end faces of the rotor 4, a rotor post seal 24 which is located around the central shaft 2 of the inlet and outlet of the air A and the gas G, a ring-like bypass seal 26 which is located on an outer peripheral edge on the upper and lower end faces of the rotor 4, and an axial seal 28 which is vertically located at an outer peripheral portion of the rotor 4 so as to seal the air side and the gas side.
On the other hand, the conventional rotary type regenerative heat exchanger 1 is provided with the following seals at the housing 6 side; more specifically, a sector plate 30 which is located facing the upper and lower end faces of the rotor 4 so as to seal a space between the air side and the gas side in the upper and lower end faces of the rotor 4, and an axial plate 32 which is vertically located along an outer peripheral portion of the rotor 4 so as to seal the air side and the gas side.
In the conventional rotary type regenerative heat exchanger 1 having the structure as described above, the radial seal 22, rotor post seal 24, bypass seal 26 and the axial seal 28, which are attached to the rotor 4, slidably move on the sector plate 30 and the axial plate 32 fixed to the housing 6, and a leak has been prevented by a mechanical contact of these plates with seals. However, according to the aforesaid structure such that the leak is prevented by a mechanical contact, in the case where the rotor 4 thermally deforms, and then, a gap between the plate and the seal becomes a state different from a design value, there has arisen a problem that sufficient seal effect is not obtained.
Further, as shown in FIG. 7, by a generation of the air bypass leak ABL, a low temperature air A on the inlet and a high temperature air A on the outlet are mixed in the rotary type regenerative heat exchanger 1. As a result, the temperature of air A on the outlet lowers as compared with the case of no leak. For this reason, the temperature of the combustion air A supplied to the boiler 18; as a result, there has arisen a problem that the heat efficiency of the boiler 18 is lowered by the decrement in temperature.
Moreover, as shown in FIG. 7, by a generation of the gas bypass leak GBL, the quantity of gas which is used as a heating fluid decreases in the rotary type regenerative heat exchanger; as a result, there has arisen a problem that the heat efficiency of the boiler 18 is lowered by the decrement in quantity.